OK - here's a new Slant 6 article in Hot Rod (checked the date this time - Aug 2017 ;-))

There's enough detail in the valvetrain info to know this; that's an extreme amount of valve-side reduction in valvetrain mass, esp. for such small OE sized componentry.
The effect on output would be definite.
A modern grind would make better torque down low, approx the same peak, meaning nice wide curve......but would need more spring to control so............
DI & EFI ? Unless there is some misfire low spark energy issue, peak full throttle hp prob not much, driveability & mpg....would be a plus for sure. EFI only offers the same
as with other like builds, better hp#'s from improved distribution 10-20hp, but again the drive/economy plus is what it is. With this engine, economy probably isn't high on
the wish list.:) That's a Hueege freakin' cam for a slanty........................